Ball-point pen tip

ABSTRACT

A ball-point pen tip provided with a tubular ink guide portion formed of metal. The ink guide portion is formed with radial projections extending radially inwardly produced by the pressing deformation of the metal tube. These projections define capillary channels between neighbouring projections and a ball seat at their radially oriented surfaces. An ink guide stem disposed in the tubular ink guide portion has one end in contact with at least one of the projections, and has the other end confronting with an ink supply stem inserted in a holder. The holder and the ink guide portion provide a socket of the pen tip. Such pen tip is applied to a ball-point pen which includes an ink reservoir adapted to be connected to said ink supply stem. Such ball-point pen employs an aqueous solution based low viscosity ink.

This is a Continuation of application Ser. No. 109,375, filed Jan. 3,1980 (now abandoned).

BACKGROUND OF THE INVENTION

This invention relates to a ball-point pen tip and a ball-point penprovided with the same, and more particularly, to a type thereof whichuses an aqueous solution based low viscosity ink.

According to the conventional ball-point pen, a tip portion includes asocket formed of plastic material or metal such as brass and nickelsilver, and a steel or rubby-ball rotatably disposed in the tip portionof the socket. Further, an ink guide stem is inserted in the rearportion of the socket, and an ink passage is formed between a ball seatand the ink guide stem.

In this type of the pen tip, the socket must stably hold the ball, evenwhen large writing force is applied to the pen tip. Further, in order toprovide confortable writing for long duration, the ball seat mustsustain frictional wear due to the rotational surface contact with therigid ball. Furthermore, ink must be constantly supplied into the ballseat and the ink passage in conformity with the consumption amount ofthe ink, so that the ink passage must provide sufficient cross-sectionalarea so as to permit the ink to pass therethrough and must createcapillary action for retaining the low viscosity ink therein so as toprevent the ball-point pen from failing to write or skipping.

In case the socket made of plastic material is used, it is possible toproduce axial channels, as the ink passages, having complicatedcross-sectional shape by molding in order to create sufficient capillaryaction. However, the ball seat is extremely worn due to rotationalcontact with the ball, to thus degrade writing performance for longduration. Further, the plastic socket does not provide sufficient forcefor holding the ball therein in comparison with the metal socket, sothat ball may be accidentally released or disengaged from the ball seatduring writing.

On the other hand, in case the socket made of metal is used, it would bedifficult to produce a plurality of axial channels, as the ink passages,to create capillary action. Generally used are copper alloys such asbrass and nickel silver those being easily subject to machining orcutting. However, it is yet difficult to produce axial capillarychannels by machining, and resultant socket is costly with lowproductivity. Further, since brass and nickel silver are apt to becorroded by the aqueous solution ink, the ink to be used must beselected in light of its characteristics such as pH and Cl-ion content,resulting in reducing variety of the aqueous solution ink.

Another type of socket of ball-point pen is proposed in U.S. Pat. No.3,781,123, wherein a central axial bore having simplified circularcross-section is formed instead of the plurality of axial channels forcapillary action. The central bore has one end in communication withradial grooves each having capillary dimension and radially spreading inthe surface of the ball seat. However, according to this type, in casethe central bore has relatively large diameter so as to supply largeamount of ink, reduced is the capillarity for maintaining capillaryaction of the aqueous solution based low viscosity ink, and therefore,such socket may not be appreciated as a ball-point pen tip which usesaqueous solution ink.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to overcome theabove-mentioned drawbacks and to provide an improved ball-point pen tipand the ball point pen provided with the tip which uses an aqueoussolution based low viscosity ink, wherein a socket provides excellentball retainability and sustains frictional wear due to rotationalcontact between the ball seat and the ball, yet providing smoothintroduction of the ink into the ball seat by the axial capillarychannels, to thereby prevent the ball-point pen from failing to write orskipping.

These and other objects are attained in accordance with the presentinvention by providing a socket comprising a holder formed with openingsand a tubular ink guide portion made of metal whose hollow space is incommunication with one of the openings of the holder. The tubular inkguide portion is formed with a plurality of protrusions radiallyinwardly bent toward the central axis of the tube at the samecircumferential position thereof by the pressing deformation of themetal tube. Between the neighbouring protrusions, ink passages areradially provided for capillary action. The ball is rotatably supportedbetween the walls of the inwardly bent protrusions and tip end of thetubular ink guide portion with a part of the ball surface being exposedto the atmosphere. Further, the other opening of the holder allowsinsertion of an ink supply stem therethrough. The ink supply stem is incontact with one end of an ink guide stem disposed in the tubular inkguide portion. The other end of the ink guide stem is in contact with atleast one of the protrusions radially inwardly extended.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings;

FIG. 1 is a longitudinal cross-sectional view of a ball-point pen tipaccording to a first embodiment of the present invention;

FIG. 2 is a longitudinal cross-sectional view of a ball-point pen tipaccording to a second emboidment of the present invention;

FIG. 3 is a longitudinal cross-sectional view of a ball-point pen tipaccording to a third embodiment of the present invention;

FIG. 4 is a transverse cross-sectional view taken along the line IV--IVof FIG. 1;

FIG. 5 is a transverse cross-sectional view taken along the line V--V ofFIG. 2;

FIGS. 6 thru 10 are longitudinal cross-sectional view of variousexamples of protrusions extending radially inwardly according to thepresent invention;

FIG. 11 is a transverse cross-sectional view taken along the line XI--XIof FIG. 2;

FIGS. 12 and 13 are transverse cross-sectional view showing anotherembodiments of ink quide stems, and

FIG. 14 shows a longitudinal cross-sectional view showing a ball-pointpen provided with a ball-point pen tip according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and initially to FIG. 1, an ink guideportion 2 is integrally formed with a holder portion 3 to define a metalsocket 1. An ink supply stem 7 is inserted into a rear opening of theholder 3 and contacts with an ink guide stem 6 disposed in the ink guideportion 2. The tubular ink guide portion 2 made of metal is formed witha plurality of projections 5 extending radially inwardly. Theseprojections 5 are formed by radially inwardly bending the metal tube 2at the same circumferential position thereof. A ball 4 is rotatablysupported between a ball seat 9 defined by side walls of the protrusions5 and a tip end of the tubular ink guide portion 2. The tip end isradially inwardly bent.

As shown in FIG. 4, three radially inwardly bent projections 5 defineink passages 8 (capillary channel) therebetween for capillary action.

A second embodiment according to the present invention is shown in FIG.2, wherein like parts and components are designated by the samereference numerals as those shown in the first embodiment. According tothe second embodiment, a tubular ink guide portion 2' made of metal isindependently formed with respect to a holder 3' to provide a socket 1'by the combination thereof. A plurality of projections 5 are formedwhich radially extend into the central axis of the tube 2'. As shown inFIG. 5 the projections 5' are defined by four radially inwardly bentportions between which ink passages 8 are provided. Further, in thetubular ink guide portion 2, a rod having a complicated cross-section asshown in FIGS. 11 through 13 is disposed as an ink guide stem6'(6",6"'). The rod is formed with axial clearances to permit ink forcreating capillary action.

A third embodiment of this invention is shown in FIG. 3, wherein atubular ink guide portion 2 is formed integral with a holder 3 toprovide an integral socket 1, and further, the ink supply stem isintegral with the ink guide stem to provide an integral ink supply stem7'.

As mentioned the above, the socket 1 or 1' of the present invention canbe provided in integral structure, or by connecting the tubular inkguide portion to the holder independently formed relative to the tubularink guide portion. However, in both cases, at least the tubular inkguide portion should be formed of metal, while the holder is formed ofeither synthetic resin or metal. Since ink guide portion of the socketis formed in the metal pipe, the ball 4 is sufficiently supportedtherein, and the ball seat 9 has sufficient wear resistance againstrotational contact of the ball for long duration. Further, capillarychannels 8 in fluid communication with the ball seat 9 are easilyprovided by pressing deformation of the metal tube 2 radially inwardlyat the same circumferential portion thereof to provide projections 5extending radially inwardly. The metal for use in the tube 2 is forexample, copper alloy such as brass and nickel silver, those beingsubject to easy machining, or stainless steel which has been consideredto be difficult to use due to difficulty in machining.

By the formation of the radial projections 5, radial ink passages 8(capillary passages 8) are defined, so that ink supply amount can beincreased, and ink retainability is enhanced to thus provide uniform inksupplying function into the ball seat without causing any disadvantagessuch as skipping.

The size and numbers of the protrusions 5 are determined by the diameterof the metal pipe 2, the diameter being determinative by the diameter ofthe ball 4. Specifically, in order to create capillary action conductedin the spaces between the projections 5, three to six projections areformed, preferrably, three to four projections. The distance between theprojections (width of the passages 8) is in a range of about 0.01 mm to0.6 mm, preferrably 0.02 mm to 0.4 mm.

Further, the ball 4 is an ordinary steel ball or rubby ball. Thediameter of the ball 4 is in a range of 0.5 mm to 1.5 mm. Among these,widely used are the balls having diameters of 0.5 mm, 0.7 mm, 0.8 mm and1.0 mm. The ball 4 is rotatably supported between the ball seats 9defined by the projections 5 and a tip end of the metal tube 2 radiallyinwardly bent.

The ink guide stem 6(6') which serves to supply ink into the capillarychannels 8 is formed of resin finished fascicular synthetic fibers, orfoamed plastic stem or synthetic resin stem. The ink guide stem ispreferrably formed or plastic stem in light of easiness of molding. Inthis case, since the ink is flown through the spaces defined between theinner peripheral surface of the metal tube 2' and the ink guide stem 6'as shown in FIG. 2, the plastic ink guide stem 6' is formed withcapillary grooves as at 10 (FIGS. 11 to 13) along the axial direction ofthe stem 6' in order to ensure introduction of the ink into thecapillary passage 8. These grooves 10 are provided by forming the outersurface of the stem 6' in complicated configuration. Such plastic stem6' is produced by extruding plastic materials such as polyacetal, nylonand cellulose derivatives.

As shown in FIG. 14, a ball-point pen includes a tip portion 11, a penshaft 12 and an ink reservoir 13. When the ball-point pen tip of thepresent invention is accomodated in the ball-point pen which usesaqueous solution ink, the ink supply stem 7 serves to introduce the inkfrom the ink reservoir 13 to the ink guide stem 6, so that the inksupply stem is required to provide sufficient function for supplyingsufficient amount of ink in accordance with writing speed. In view ofthe above, the diameter of the ink supply stem 7 is larger than that ofthe ink guide stem 6, and the ink supply stem 7 is rod shape, and isformed of resin finished fascicular fibers, or formed of plastic moldedarticles having continuous bubbles therein, or plastic molded articleformed with a plurality of axial bores therein. Since the ink guide stem7 is formed with a plurality of generally straight axial bores from oneend to the other, the stem of the resin-finished fascicular fibers isthe most advantageous in terms of the ink transferring speed and supplyamount thereof. Such resin finished fascicular fibers is produced bypartially bonding fibers with resins, those fibers being nylon oracrylic or polyester synthetic fibers having denier number of 3 to 10d.These fibers are in the form of fascicular oriented along axialdirection of the stem 7.

Such ink supply stem has one end inserted into the rear opening of thesocket 1 in order to provide surface contact with the ink guide stem 6.Alternatively, the rear end portion of the ink guide stem 6 is thrustedinto the ink supply stem 7, or minute clearance is provided between theink supply stem and the ink guide stem 6.

Further, as shown in FIG. 3, the ink supply stem 7 can be formedintegral with the ink guide stem 6 so as to gradually reduce thediameter toward the pen tip. The integral material is, for example,resin finised fascicular fibers or plastic molded article formed withcontinuous bubbles.

FIGS. 6 through 10 show embodiments showing the various shape of theprojections 5 and the ball seat 9. According to the embodiment shown inFIG. 6, the ball seat 9 provides point contact with the ball 4, whereasaccording to the embodiment shown in FIG. 7 the ball seat 9' providesline contact therewith. Further, according to the embodiment of FIG. 9,the ball seat 9"' provides surface contact with the ball 4, as in thecase of the embodiment shown in FIG. 8 wherein a ball seat 9" providesurface contact with the ball 4. In case light or smooth writingperformance is required, the contacting area between the ball and theball seat should be minimized. On the other hand, if the ball-point penis put much weight on continuous ink lay-down, contacting area betweenthe ball and the ball seat should be large.

FIG. 10 shows still another embodiment of the protrusions 5, whereinaxial length of one of the projections 5' is longer than that of theremaining projections 5 with respect to their rear faces. In this case,since the ink guide stem 6 is contacted with the side face of the longerprojections 5', clearance space is formed between the ink guide stem 6and noncontacting projections 5, so that ink is accumulated in thespace. This ink accumulation provides smooth ink supplying action to theball, to thus avoid ink separation in the ink passages.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A ball-point pen using low viscosity aqueous ink,comprising; a metallic tubular ink guide portion formed with a pluralityof radially inwardly extended projections to provide a ball seat and todefine ink capillary passages therebetween, a metallic ball having adiameter of 0.5-1.5 mm rotatably secured between said ball seat and tipend of said ink guide portion, a holder having both ends formed withopenings and an ink feeder, said ink guide portion being formed ofstainless steel having its rear end inserted into one open end of saidholder, said ink feeder comprising an ink guide stem formed of plasticrod and, an ink supply stem formed in a rod shape having a largerdiameter that that of said ink guide stem and being formed of fascicularfibers partially bonded together with resin, one end of said ink supplystem inserted into the other end of said holder, said ink guide stemdisposed in and projecting through said ink guide portion to providecapillary channels defined between said ink guide stem and an innersurface of said ink guide portion, said ink guide stem having one end incontact with said projections but spaced from said ball and the otherend in contact with said end of said ink supply stem in said holder tosupply low viscosity aqueous ink from said ink supply stem to said ballthrough said capillary passages.
 2. The pen of claim 1 wherein saidinwardly extended projections provide point contact with said metallicball.
 3. The pen of claim 1 wherein said inwardly extended projectionsprovide line contact with said metallic ball.
 4. The pen of claim 1wherein said inwardly extended projections provide surface contact withsaid metallic ball.
 5. The pen of claim 1 wherein said fascicular fibersof said ink supply stem are oriented along an axial direction of saidink supply stem.
 6. A ball-point pen using low viscosity aqueous inkcomprising; a pen shaft, an ink reservoir contained in said pen shafthaving a supply of low viscosity aqueous ink, a ball-point pen tipsecured in one end of said pen shaft comprising a metallic tubular inkguide portion formed with a plurality of radially inwardly extendedprojections to provide a ball seat and to define ink capillary passagestherebetween, a metallic ball having a diameter of 0.5-1.5 mm rotatablysecured between said ball seat and tip end of said ink guide portion, aholder having both ends formed with openings and an ink feeder, the saidink guide portion being formed of a wear resistant metal and its rearend inserted into one open end of said holder, said ink feedercomprising an ink guide stem formed of plastic rod and an ink supplystem formed in a rod shape having a larger diameter than that of saidink guide stem and being formed of fascicular fibers partially bondedtogether with resin, said ink supply stem having one end inserted intothe other open end of said holder and the other end inserted into saidink reservoir, said ink guide stem disposed in and projecting throughsaid ink guide portion to provide capillary channels defined betweensaid ink guide stem and an inner surface of said ink guide portion, saidink guide stem having one end in contact with said projections butslightly spaced from said ball and the other end in contact with the endof said ink supply stem in said holder to supply ink from said inkreservoir through said ink supply stem and said capillary channels intosaid ink capillary passages to said ball.
 7. The pen of claim 6 whereinsaid inwardly extended projections provide contact with said metallicball.
 8. The pen of claim 6 wherein said inwardly extended projectionsprovide line contact with said metallic ball.
 9. The pen of claim 6wherein said inwardly extended projections provide surface contact withsaid metallic ball.
 10. The pen of claim 6 wherein said fascicularfibers of said ink supply stem are oriented along an axial direction ofsaid ink supply stem.
 11. The pen of claim 6 wherein said ink guideportion is formed of stainless steel.